Let me complete your question:
Find the missing coefficient in the equation of the line that passes thru given point. Ax+3y=5, (2-1)?
Is this the question?
A= 4
4x+3y=5
you plug in your points to solve it.
A(2) + 3(-1) = 5
2A + -3 = 5
2A= 8
A = 4
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