Averqge speed of the car = 45 miles/hr, which means,
The car travels 45 miles in 1 hr.
Using unitary method,
The car travels 45 miles in 1 hr
The car would travel 1 mile in 1/45 hrs
The car would travel 90 miles in 1/45×90 hrs
So, calculating this,
1/45×90 = 2 hrs