have to find the exact value(so in fraction form.. like 1231231/41231 or something) of 2/3 + 3/4 - 2/11 - 5/21

Question

I'm unsure of the working

Answer 1

2/3 + 3/4 - 2/11 - 5/21
3*4*11*7 = 924, so if we use that as our common denominator, the numerators add up to:

2*(4*11*7) + 3*(3*11*7) - 2*(3*4*7) - 5*(4*11) = 921

921/924 = 307/308