Question

What is the value of the function when x = 4? y = 3x + 7

Answer 1

2x - 3y = 7 and -3x + y = 7..multiply Equation 2 by THREE and add to Equation 1
-9x + 3y = 21...........................watch the y's disappear
-7x........ = 28
x = -4
substitute -4 instead of x in either of the ORIGINAL equations

2x - 3y = 7
2(-4) - 3y = 7
-8 -3y = 7..........add 8 to both sides
-3y = 15
y = -5

im not sure

Answer 2

$y=3x+7\ \ \ | substitute\ x=4\\\\ y=3*4+7\\\\ y=12+7=19\\\\ Value\ of\ function\ is\ 19.$