SAT Systems of two linear equations in two variables Practice Question 18 (Hard)

Question bank / Systems of two linear equations in two variables

Math · AlgebraHard

$0.2x + 0.5y = 7.1$
$0.3x - 0.4y = -2$
If $(x, y)$ is the solution to the system of equations above, what is the value of $5x + y$ ?

$19$

$35.5$

$51$

$71$

Show answer and explanation

Answer: C

Adding the two equations gives $0.5x + 0.1y = 5.1$ . Multiplying by 10 gives $5x + y = 51$ . (Solving fully gives $x = 8$ and $y = 11$ , and $5(8) + 11 = 51$ .)

Choice A is $x + y$ , not $5x + y$ .

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