A chef had 40 apples and 54 peaches. After making some pies, he had 39 apples left. How many apples did he use?
First, we need to find the total number of fruit the chef had. The chef had 40 apples and 54 peaches, so the total number of fruit is 40 + 54, which is 94. 

Next, we need to find the total number of fruit the chef had after making some pies. The chef had 39 apples left, so the total number of fruit is 39 + ?. We don't know how many peaches the chef had left, so we'll call that number x. 

Now, we need to set up an equation to solve for x. We know that the total number of fruit before making pies is 94 and the total number of fruit after making pies is 39 + x. We also know that the total number of fruit after making pies is 94, so we can set up the equation 94 = 39 + x. 

We can solve this equation by subtracting 39 from both sides. When we do that, we get 55 = x. This means that x is equal to 55, so the chef had 55 peaches left. 

Now, we can plug 55 in for x in our equation 39 + x. When we do that, we get that 39 + 55 is 94. This means that