40 fifth graders take a bus to school. 8x8= 64 so they have you a good fraction to start with to find out how many kids are walking or taking their bike (3/8) all you have to do is multiply 3 and 8 which equals 24 to find the fraction of the amount of kids who take the bus you subtract 3 from 8 which gives 5/8 and to get the answer you multiply 5 and 8 which is 40.
Area is supposed to be multiplied by 2.
7n + 3 = 3n + 27
7n -3n =27-3
4n =24
n= 6.