Please how to solve this problem for grade 2

Three times the sum of a number and seven is negative thirty-six. what is the number?

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?

Which of the following vectors are orthogonal to (2,1)? check all that apply