Question

numbers 4 and 7 please

Answer 1

For your #4, you did it correctly. 
t^-4(t^-5) = 1/(t^9)

For 7), multiply 4 and 2 together

4 x 2 = 8

t^8 is your answer

hope this helps

Answer 2

The answer for 4 is t ^-9 and the answer for 7 is (am not that sure) 32