Let's solve your system by substitution. y = − 2 x + 7 ; y = 5 x − 7
Step: Solve y = − 2 x + 7 for y: y = − 2 x + 7
Step: Substitute − 2 x + 7 for y in y = 5 x − 7 : y = 5 x − 7 − 2 x + 7 = 5 x − 7 − 2 x + 7 + − 5 x = 5 x − 7 + − 5 x (Add -5x to both sides) − 7 x + 7 = − 7 − 7 x + 7 + − 7 = − 7 + − 7 (Add -7 to both sides) − 7 x = − 14 − 7 x − 7 = − 14 − 7 (Divide both sides by -7) x = 2
Step: Substitute 2 for x in y = − 2 x + 7 : y = − 2 x + 7 y = ( − 2 ) ( 2 ) + 7 y = 3 (Simplify both sides of the equation)
