solve by substitution.. how do you solve this equation. 15x-20y=5  5y=2+5  text example is confusing me.

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A neat way to solve this problem where15x - 20y = 5, and5y = 2 + 5, is to first solve the second equation for y:5y = 7, multiply both sides of the equation by the inverse of 5, 1/5:5y (1/5) = 7(1/5); perform multiplication operation to yield y = 7/5, now substitute the value of y into the equation:15x -20(7/5) = 5; perform multiplication operation:15x - 140/5 = 5; eliminate 140/5 from the equation's left side: 15x - 140/5 + 140/5 = 5 + 140/5; simplify:15x = 25/5 + 140/5; 15x = 165/5; isolate x by multiplying by the reciprocal of 15; 1/15(15x) = 165/5(1/15); simplify: x = 165/75; simply:x = 11/5