Which is not used to reach conclusion in a formal proof? 1. inductive reasoning 2. true premises 3. logic 4. postulates or previously proven theorems

Me because some of question i don’t understand

Prove that quadrilateral is a rhombus.

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?