Chissy had 4 gallons of gas in her tank when she arrived at the gas station. She pumped gas into her car at a rate of 3/10 gallon per second. How many gallons of gas were in the tank after s second?

4 + (3s/10) gallons

Step-by-step explanation:

Originally, there are 4 gallons. Add that to the expression. Every second, 3/10 gallon are filled. So s times 3/10 equal the total number of gallons added. Add both expressions together to get the answer.