Answer:
26.59 minutes
Step-by-step explanation:
Let's say the time needed to do the driveway combined is x. Sue does y parts of the driveway, and Tom does z parts of the driveway. Combined, y + z = 100% = 1, as they finish the whole driveway.
Next, Tom will take 45 * z minutes to do his part of the driveway. For example, if he did 50% = 0.5 of the driveway, he would take 45 * 0.5 = 22.5 minutes to do it. Similarly, Sue will take 65 *y minutes to do her part of the driveway. Since they will finish at the same time, we can say
45 * z = 65 * y
y + z = 1
Therefore, if we subtract y from both sides of the second equation, we have
z = 1-y
We can then plug 1-y in for z in the first equation to get
45 * (1-y) = 65 * y
45 - 45*y = 65*y
add both sides by 45 * y to separate the y values and their coefficients
45 = 110 * y
divide both sides by 110 to find y
y = 45/110 = 0.409
Use 1-y=z to get z = 1-0.409 = 0.59
Therefore, 45*z = 26.59 = 65*y
