How can i work this out or solve this?

Christina can paint 420 square feet in 105 minutes. which unit rate describes the scenario?

Given the sequence 7, 14, 28, 56, which expression shown would give the tenth term? a. 7^10 b. 7·2^10 c. 7·2^9

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