Question

solve(3/4x=1/5, x=_)

Answer 1

I'm not sure if you mean:

3/(4x) = 1/5

or

(3/4)x = 1/5

Let's do both, just to be sure.
Starting with the first one:

3/(4x) = 1/5
3 = 4x/5
15 = 4x
x = 15/4

The second:

3x/4 = 1/5
3x = 4/5
x = 4/15