Hello jello

Welcome to Math Help Forum!You haven't got this expression quite correct - there's a missing right parenthesis somewhere. If it should come just before the = sign, then what you mean is:

1/ ((0.25/30)+(0.25/20)+(x/15)+(1-(0.5+x))) = 10

in which case the equation is:

Multiply top and bottom of the LHS by , and remove the inner pair of brackets from , noting the minus sign in front of the :

(to 4 d.p.)

Grandad