12-3=9
30+7=37
I believe you just plug in any two numbers that will come out to 9 when subtracted or 37 when added.
Two positives make a positive
two negatives make a positive
1 negative and 1 positive make negative
1 positive and 1 negative make a negative
3x = 20.40. Divide each side by 3.
x = 6.8
she earns $6.8 per hour
-7x-5y=-47x+9y=-4
combine like terms to cross out the 7x
solve for y, to get -2
plug it back in to one of the equations and x is 2
y=-2
x=2