tommy sells 3 candy bars a day. he sold a total of 180 bars. how many days did he sell the candy bars? the days is unknown. what equation represents this information?

a. 3+x+180
b. x-3+180
c. 180x+3
d. 3x+180

i think the answer is d but i am not sure!

Lin is writing an equation to model the proportional relationship between y, the total cost in dollars of downloading videos from a website, and x, the number of videos downloaded. she knows that the total cost to download 3 videos was $12. her work to find the equation is shown below. joylin’s work step 1 k= 3/12= 0.25 step 2 y= 0.25x where did joylin make her first error?