breaking the codes

$ - @ = 9
@ * $ = 48
@=_____ $=_______
we can't figure this one out

This is well above the ability of 4th graders. I suspect the second line was meant to be =36, then the answers would have been 3, 12

As it is, the answers are irrational, which is not something one would want even to give an 8th grader in Algebra.