Janet's car insurance payment decreases by $20 each year. Which expressions represent the total change in her payment over 5 years? 20 - 20 - 20 - 20 - 20

I'd say you could do t-20y where t is the amount she pays at year 0 and y is the amount of years that pass. For example say Janet originally payed $200 at year zero, that would be your t variable. Five years later (y variable is now 5) you would say 200-20 (5) which would be 200-100 = 100