I believe the SSS theorem as they both share/have side measurements (and no defined angles)
4y = - 2x + 12
y = - 2/4x + 3
The y intercept is 3
57.6² = 33.8² + QR²
QR² = 2.175,32
QR = 46.64
57.6/sen90º = 46.64/sen(P)
sen(P) = 46.64*sen90º/57.6
sen(P) = 0.809
angle P is sen^-1 = 54.06º ≈ 54.1º
Addition bc. you need adding to both sides x and will get this result of 3x+2 = 11
hope helped