The element which becomes deficit in acidic conditions

Solve: 1/x + 1/y = 5/2 and 1/x – 1/y = 1/6

If (a + b) = 9 and ab = 14, find the value of (a² + b²).

Simplify:
6x + 8y - [(12x + 6y) - (4x + 3y) + 2y] - 4x

If x + y + xy = 118, such that x < y and both 'x' and 'y' are positive integers, then find minimum value of (x + y) .

If p = 32 - q - r and pq + r(q + p) = 255, then find the value of (p² + q² + r²).

Simplify:
4x + 6y - [(8x + 5y) - (3x + 2y) + 3y] - 2x

1/3 + 1/15 + 1/35 + 1/63 + 1/99 = ?

Calculate the value of the expression: {2 X (P³ - Q³) - 30 X P X Q} if (P - Q) = 6 and (P² + Q²) = 80