Answer:
1 / y^22
Step-by-step explanation:
We multiply bracket powers and add powers if no brackets when multiplying same numbers on same line (denominator with denominator and numerator with numerator, we could cross multiply with (y^7)^6 / (y^7)^6 but workings below show when we simplify then subtract powers last step to reduce the fraction with no action of cross multiply.
(y^4 )^5 = y^20
(y^7)^6 = y^42
= y^20/ y^42
= 1 / y^22
