To solve this, you must first find out how long it would take Sasha to mow 1/8 of an acre. We know that it takes her 45 minutes to mow 3/8 of an acre, we we can base off of this. Assuming that her rate of mowing is constant, we simply have to divide 45 by 3, since we know that it takes her exactly the same amount of time to mow the same amount of grass every time. Therefore, we can divide the 45 by 3 in order to find the amount of time it would take her to mow 1/8 of an acre of grass.
45 / 3 = 15
So it takes Sasha 15 minutes to mow 1/8 of an acre of grass. Now, we just have to figure out what the variable in the equation would be.
If 1/8x = 15, and 3/8x = 45, then we understand that for every 1/8 of an acre Sasha mows, she adds 15 minutes to her time. So now, all we need to do is multiply by 4 (since 4 * 15 = 60, and there are 60 minutes in an hour).
(1/8x) * 4 = (15) * 4
4/8x = 60
So, we are left with 4/8, which reduces to 1/2.
In one hour, Sasha can mow 1/2 acre of grass.
Hope that helped =)