The answer is 26, but I dont know how to solve it

First of all move all the Xs to the left side, and the numbers to the left.
So
x/2-x = -13
Which means
X/2-x/1 = -13
Which means x/2-2x/2 = -13
So u combine to two fractions
-x/2 = -13
-x = -13 * 2
Which means x = 26 (u flip the negativity)

Well in order to lose a pound you would have to burn 1,500 calories. the more calories you burn the more weight you lose. in order to lose 2 pounds you would have to run 4 hours and 28 minutes.