The line

Can be written as:

This is the same line in the slope-intercept form:

Then, the original line has an slope of -2.
To find the slope of a perpendicular line to this one we need to remmeber that two lines are perpendicular if and only if

Plugging the value of the original line we have:

Therefore a line perpendicular to the line 10x+5y=10 has slope 1/2 or 0.5.