Now that we know how to evaluate expressions, we're going to look at how to evaluate formulas. Now we see formulas in many different types of situations. We might see them in geometry when we're looking at the formula on how to calculate area. We might see them in science when we we find the formula for the force of an object. You can see formulas in many different situations. A formula is an expression or an equation that is used to solve a problem. And many times the problems are based on real life situations. So we're often going to have these type of problem given to us as a word problem. So look for this information when you're reading the word problem. First, look for the formula. Second, figure out what the variables represent. And then third, figure out what numbers you're being told to use to substitute for the variables in the formula. So let's look at an example together. The formula for finding the area of a triangle is one half BH, where B is the base and h is the height of the triangle. Find the area of a triangle that has a base of ten and a height of three. First, let's look for our formula. We're told our formula is one half BH. And we know that when we have a number written next to a variable, it means they're being multiplied. Well it’s the same thing when we have more than one variable next to each other as well, it means these are all being multiplied together. Next, we want to know what those variables represent. We're told that B represents the base and that H is the height of the triangle. So let's put all this information together in our workspace. So our formula is one half BH and we know that B is the base and H is the height. It is very, very important to make sure that you can find this information in your word problem. Next, we can actually solve the problem and find the area as they're telling us to. So we're told to find the area of a triangle that has a base of ten and a height of three. So now we have the actual numbers that we're going to use to substitute into our formula. We're going to put ten in for B for the base and three will get substituted for the h for the height. And it will look like this. So now instead of one half times B times h, we have one half times ten, times three. And now since since we have an expression that has just numbers in it, we can go ahead and simplify this. So one, two times ten will give us five and then five times three will give us 15 as our final answer.