Question

Use multiplying by 1 to find an expression equivalent to nine fifths with a denominator of 10b.

Answer 1

1 = 2/2
Therefor if we multiply 9/5 by 2/2 we will get 18/10
Basically figure out what denominator you need and then find a suitable value of 1, where in this case 5*2 = 10 :)