# How do you evaluate -x+y given x=1/2 and y=-2/5?

Nov 9, 2016

$- \frac{9}{10}$

#### Explanation:

Substitute 1/ for $x$ and $- \frac{2}{5}$ in the given formula and then solve using mathematics:

$- x + y \implies - \frac{1}{2} + \left(- \frac{2}{5}\right) \implies - \frac{1}{2} - \frac{2}{5}$

Next get each term in the formula over the same denominator by multiplying by the correct form of $1$:

$- \frac{1}{2} - \frac{2}{5} \implies \left(\frac{5}{5}\right) \left(- \frac{1}{2}\right) - \left(\frac{2}{2}\right) \left(\frac{2}{5}\right) \implies - \frac{5}{10} - \frac{4}{10}$

Next add together the fractions, in this case adding together negative numbers:

$- \frac{5}{10} - \frac{4}{10} \implies - \frac{9}{10}$