Hello MckenzieMoore25, first you would need to solve for x for both equations which then you can plugin and easily find m. Hopefully this can guide you to the answer your looking for! :)
equate m=m 10x+4=5x-4 subtract 4 from both sides, 10x+4-4=5x-4-4 10x=5x-8 subtract 5x from both sides 10x-5x=5x-5x-8 5x=-8 divide 5 on both sides 5x/5=-8/5 x=-8/5