Big al, the ape, ate 100 bananas from may 1 through may 5. each day he ate six more bananas than on the previous day. how many bananas did big al eat on may 5?

Set up an expression.
Each day he ate 6 more bananas, so

x will be the number of bananas he ate on the first day.
x + (x+6) + (x+6+6) + (x+6+6+6) + (x+6+6+6+6) = 100
5x +60 = 100
5x = 40
x = 8

Now on the 5th day, May 5, he ate (x+6+6+6+6), which is (8+6+6+6+6+6), which equals 38.
On May 5, he ate 38 bananas.