Lucy is knitting a blanket and needs to buy some more yarn. At her local craft store, 2 skeins of yarn cost $7 and 8 Skeins of yarn cost $28. Which equation represents this direct variation

Where y is the cost and x is the number of skeins of yarn.

Step-by-step explanation:

To model this situation we can use the linear equation:

Where y is the cost, x is the number of skeins of yarn, a is the slope of the equation and b is the y-intercept.

If 2 skeins of yarn cost $7, we have that:

If 8 skeins of yarn cost $28, we have that:

Multiplying the first equation by 4 and subtracting the second equation from it, we have:

Now, finding the value of a, we have:

So our equation is:

step-by-step explanation: