y = 7 + x
y = 3x + 9
To solve the simulataneous equation with subtraction,
Step 1: name the equations
y = 7 + x ---- equation 1
y = 3x + 9 ----- equation 2
Step 2: subtract equation 1 from 2
so that
y - y = (3 x -x ) + (9 - 7)
0 = 2x + 2
2x = - 2
divide oth sides by 2
x = -2/2
x = -1
To get y, substitute the value for x into equation 1
y = 7 + x
y = 7 + (-1)
y = 7-1 = 6
y = 6
hence the solution is (-1, 6)