x = 2, y = 8
4x + 8y
= 4(2) + 8(8)
= 8 + 64
= 72
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4x + 8y = 20-4x + 2y = -30First add equations 1. & 2. to get:(4x + -4x) + (8y + 2y) = 20 + -30⇒ 10y = -10⇒ y = -1Multiply equation 2. by 4 and subtract it from equation 1:4x + 8y = 20-16x + 8y = -120⇒ (4x - -16x) + (8y - 8y) = 20 - -120⇒ 20x = 140⇒ x = 7Solution x = 7, y = -1Alternatively, to find x, now that y is known to be -1:Substitute y = -1 into equation 1. to give:4x + 8(-1) = 20⇒ 4x -8 = 20⇒ 4x = 28⇒ x = 7The solution can be checked y substituting the values found for x and y in to equation 2. and checking it is the correct value:-4x + 2y = -4(7) + 2(-1)= -28 + -2= -30as required, so the solution is correct.
2y = 4x + 4y = 2x + 2
7 + 8y - 3y + 2 =7 + 2 + 8y - 3y = 9 + 8y - 3y = 9 + 5y
X=2
2x + 2 = 4x -1 2x = 3 x = 1.5