Ummmm...I'm not sure what you're doing with the "charts" so I'll show you how I would set it up.

Call the speed of the express v. Then the speed of the bus is v - 7 (mph).

Call the time it takes the express to travel 90 miles t. Then it also takes the bus a time t to travel 75 miles. Since d = vt:

90 mi = vt (Express)

75 mi = (v - 7)t (Bus)

(I'll drop the units until the end for convenience.)

So from the first equation:

t = 90/v

Insert this into the second equation:

75 = (v - 7)*(90/v) <-- Multiply both sides by v:

75v = 90v - 630

15v = 630

v = 42 mph

v - 7 = 35 mph.

-Dan