ID: d1b66ae6
(SAT Suite Question Bank > Find Questions > Assessment: SAT + Test: Math + Domain: Algebra)
Comment: This must be one of the most straightforward level 3 (Hard) questions I have seen.
Method 1: Since the question asks about the value of y, and it is clear that the x's will eliminate using the elimination method, we can add the equations and solve directly:
-x + y = -3.5
x + 3y = 9.5
4y = 6
y = 6/4
Remember to reduce fractions or use a decimal equivalent, so either 3/2 or 1.5 are correct.
Method 2: Plug in the equations to Desmos and graph. Just make sure you input the equations correctly, signs and all. The point of intersection of the two lines clearly shows a y-value of 1.5.
Method 3: You could use substitution as a general method to tackle systems of equations, but here, that method can lead to more work than is necessary, and the greater the number of steps involved, the greater the probability of making a mistake. Also, if you want to solve for y, it makes sense to substitute for x.
-x + y = -3.5 --> y = x - 3.5 --> y + 3.5 = x
x + 3y = 9.5 --> x = -3y + 9.5
(y + 3.5) = (-3y + 9.5)
4y = 6
y = 6/4
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