y = 3x - 5
replace "y" inside the equation with "3x - 5"
6x + 3(3x - 5) = 15
distribute the 3 to both 3x and -5
3(3x) = 9x
3( -5) = -15
6x + 9x - 15 = 15
simplify
15x - 15 = 15
isolate the x
15x - 15 (+15) = 15 (+15)
15x = 30
15x/15 = 30/15
x = 2
Plug in x to one of two equations
y = 3x - 5
y = 3(2) - 5
y = 6 - 5
y = 1
y = 1 is your answer
hope this helps