What is the additive inverse of the expression below, where are a and b real numbers?

2a+b

a. -1
b. 0
c. 2a-b
d. -2a-b

Iam trying to solve a linear equation for the shoe size of someone 84" tall taking into consideration example 1 is 69" tall with a shoe size of 9 and example 2 is 72 inches tall with a shoe size of 11. i understand that the equation should be y=mx+b and that on the graph the answer is (3,2) but i just don't understand how to create the equation to solve for 84-inches and 60-inches tall questions. after two days, i need .

Item 1 solve for s. s+24=90 −114 −66 66 114

Using elimination, what is -4x+2y=-12 4x+8y=-24