You build and sell toy cars for $36 each. so far, you have built 25 toy cars. how many more toy cars will you have to build and sell to earn $1,620?

You can use the equation $36(25+t)=$1620 with t=toy cars. so first, just multiply 36*25=900 and 36*t=36t. subtract the 900 from 1,620 to isolate the variable [the equation now looks like this: 36t=720]. then, divide 36 from 720 and the answer will be 20 toy cars.