If 2x + 5y = 109 and 2x + 5 = y + 12 then y – x = ?

2x + 5y = 109 .....(i)

2x + 5 = y + 12

⇒ 2x – y = 12 – 5

⇒ 2x – y = 7 .....(ii)

On subtracting equation (ii) from (i),

2x + 5y – (2x – y) = 109 – 7

⇒ 2x + 5y – 2x + y = 102

$Rightarrow$ 6y = 102

$Rightarrow$ y = $frac{{102}}{6} = 17$

From equation (ii),

2x – 17 = 7

⇒ 2x = 24

⇒ x = 12

∴ y – x = 17 – 12 = 5