# Equation question at interview

What is the value of R in the following set of equations ?

1) $P + Q = 2$

2) $R P + Q = 5$

3) $P + R Q = 7$

one of question asked in my interview.

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Add 2) and 3) then substitute 1) to get $R \times 2 + 2 = 12$. So R is 5.