one-tenth x fewer than the sum of one-fifth y and 2x

how to I write this

1/5y +2x-1/10x

1 answer

yes, though maybe clearer as one of
1/5 y +2x-1/10 x
y/5 + 2x - x/10
(1/5)y + 2x - (1/10)x

Otherwise there's a chance to interpret it as
1/(5y) + 2x - 1/(10x)
which some people also mean. When typing online, always use enough parentheses to make it quite clear what you mean. Even an extra space or two can help.