Answer: y = 7
Explanation:
Step 1) plug in 3 for y and 9 for x in the direct variation formula, which is y = kx
3 = k(9)
Step 2) Solve for k
3 = k(9) (Divide by 9 on both sides)
3/9 = k (Now simplify 3/9)
1/3 = k. So k = 1/3
*just FYI: “k” is the constant of variation.
Step 3) use the equation y = kx and plug in 1/3 for k
y = 1/3x
Step 4) using the equation y = 1/3x, plug in 21 for x.
y = 1/3(21) (1/3*21 is the same as 21/3)
y = 21/3 (21/3 = 7)
y = 7. So that’s you’re answer! When x=21, y=7 because 7 is 1/3 of 21!
Hope this helps! My best wishes to you as you go through school!