What are the dimensions of the product matrix of two of these matrices?

In triangle △abc, ∠abc=90°, bh is an altitude. find the missing lengths. ah=4 and hc=1, find bh.

Reflect the point (7,0) across the y-axis

Kyle and elijah are planning a road trip to california. their car travels 3/4 of a mile per min if they did not stop driving, how many miles could kyle and elijah drive in a whole day? ? 1 day = 24 hours. plzzz i will give you 100 points