I need help with two step equations​

Are carpet coast $15 per square metre. the total delivery charge is $21 peter buys n squared metres of carpet what is the expression which represents the total cost in $

Idont get this question can someone me solve it? ** the distance light travels in one second (1 light second) is about 1.86 ×10^5 mi. saturn is about 475 light-seconds from the sun. about how many miles from the sun is saturn..my guess is 8.83* 10^7 you so much

Complete the equation of the line through (−10,3) and (−8,−8). use exact numbers.