Maths Olympiad Prep

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Problem 717

AMC 10/12, early questions
Geometry Difficulty 3.9 Find the answer HMMT November · United States · 2021

The graphs of the equations
y=x+8173y=289x+2021 \begin{aligned} y & = -x + 8 \\ 173y & = -289x + 2021 \end{aligned}
on the Cartesian plane intersect at (a,b)(a, b). Find a+ba + b.

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

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Official solution

Solution:
From the first equation, it is known that (a,b)(a, b) lies on the line x+y=8x + y = 8, therefore a+b=8a + b = 8.

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