Solve : 1/x+1+1/x+2= 2/x+10

I'll assume you meant

1/(x+1)+1/(x+2)= 2/(x+10)

Putting all over a common denominator, the numerator becomes

(x+2)(x+10) + (x+1)(x+10) = 2(x+1)(x+2)
2x^2+23x+30 = 2x^2+6x+4

I expect you can take it from there, eh? Just beware spurious roots that might make any of the original denominators zero. (Luckily, none in this problem)