SSC CGL 26 Oct 2014 Shift 1 Paper

999x + 888y = 1332 .... (i)
888x + 999y = 555 ..........(ii)
On adding both equations,
1887 x + 1887y = 1887
⇒ (x + y) × 1887 = 1887
⇒ x + y = 1 ....... (iii)
By equation (i) – (ii),
111x – 111y = 777
⇒ 111 (x – y) = 777
⇒ x – y = 7 ......... (iv)
∴ (x + y) (x – y) = 1 × 7
⇒ ${\mathit{x}}^2\mathit{–}{\mathit{y}}^2$ = 7