It took 3.5 hours for an airplane traveling at a constant speed of 550 miles per hour to reach its destination. what distance did the airplane travel until it reached its destination?

The formula that we want to use here is S = D/T.

S = Speed
D = Distance
T = Time

So, we know that S = 550 and T = 3.5, so we can plug them in. 

We get 550 = D/3.5 
Multiply by 3.5 on each side, and you figure out that the plane has traveled 1925 miles.