In my number the digit in ones place is double the digit in the tens place

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?

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?

Ateam has p points. p = 3w + d w = wins d = draws a) a football team has 5 wins and 3 draws. how many points does the team have?