a, 90^2/ 15^2 b, 790^4 /79^4 c, 8^14/4^12

`(90^2 )/(15^2)`

`= ((3^2 * 2 * 5)^2)/((3 * 5)^2)`

`= (3^4 * 5^2 * 2^2)/(3^2 * 5^2)`

`= 3^2 * 2^2 = 36`

`---`

`(790^4)/(79^4)`

`= ((79 * 2 * 5)^4)/(79^4)`

`= (79^4 * 2^4 * 5^4)/(79^4)`

`= 2^4 * 5^4`

`= 10000`

`---`

`(8^14)/(4^12)`

`=( (2^3)^14)/((2^2)^12)`

`= (2^42)/(2^24)`

`= 2^18`