m = 5p + 8 m = -10p + 3
m = 5p + 8
m = -10p + 3
5p + 8 = -10p + 3
5p + 8 + 10p = -10p + 3 + 10p
15p + 8 = 3
15p + 8 - 8 = 3 - 8
15p = -5
15p/15 = -5/15
p = -1/3
Check it using the given equations
m = 5p + 8
m = 5(-1/3) + 8
m = -5/3 + 8
m = -5/3 + 24/3
m = 19/3
m = -10p + 3
m = -10(-1/3) + 3
m = 10/3 + 3
m = 10/3 + 9/3
m = 19/3
m = 19/3, p = -1/3