y = kx
21 = k*3
Now use that to find x as needed.
Or, since y/x is constant (k), you can find the new x without even finding k.
You want x such that
105/x = 21/3
The value of y varies directly with x.If x=3, then y=21. Using the Direct Variation equation What is the value of x if y=105
1 answer