How do u solve 3 over 8 times a minus negative 1 over 4

If you mean (3/8) x (-1/4), then the only thing you have to do is multiply 3 times - 1. Since one of the 2 numbers is negative, that product will be negative, and 3x1=3, so 3 times - 1 equals - 3. This number goes on top of your new fraction

Then 8x4 = 32. This goes on the bottom or denominator of your fraction.

So the solution is - 3/32.