Solve (-4) - 5 + 4 + (-5)

Julie begins counting backwards from 1000 by 2’s and at the same time tony begins counting forward from 100 by 3’s.   if they count at the same rate, what number will they say at the same time?

Me get the answer and explain to me the steps to solve it would be greatly appreciated : )

What is the solution to the system of equations? 10x+3y=8 -9x-y=-20 (11, 1) (1, 11) (–1, 11) (11, –1)'