Explain how I got f(x)=57

Aline passes through 3,7 and 6,9 what equation represents the line

Julie goes to the sports store and spends $40.50 before tax. she buys a pair of shorts for $21.75 and 3 pairs of socks that each cost the same amount. how much does each pair of socks cost? $$

Siri can type 90 words in 40 minutes about how many words would you expect her to type in 10 minutes at this rate