Solve the system of equations. - 4x+7y = 20 & y=3x+15

solve for x and y using substitution

Substitute y = 3x + 15 to the equation - 4x + 7y = 20:

-4x + 7 (3x + 15) = 20 use distributive property

-4x + (7) (3x) + (7) (15) = 20

-4x + 21x + 105 = 20 subtract 105 from both sides

17x = - 85 divide both sides by 17

x = - 5

Substitute the value of x to the equation y = 3x + 15:

y = 3 (-5) + 15

y = - 15 + 15

y = 0

Answer: x = - 5 and y = 0