if you expand the parentheses this it can be written as
(y×y×y)(y×y×y) ×y^7
This shows since they are all being multiplied that you can add the exponents when they are expanded and still equal the same.. this is the same as multiplying the 3 and 2 exponents together in the original problem
y^6×y^7 do the same to these exponents add them together
y^13
