The pair of variables x=5, y=7 is the solution to the equation ax-2y=1. Find the coefficient a.

a = 3

Step-by-step explanation:

Put x = 5 and y = 7 to the equation ax - 2y = 1 and solve for a:

(a) (5) - (2) (7) = 1

5a - 14 = 1 add 14 to both sides

5a - 14 + 14 = 1 + 14

5a = 15 divide both sides by 5

5a : 5 = 15 : 5

a = 3