A loaf of bread of similar quality in the store costs $2.50.   This is the rate for a loaf of bread (the slope).  As there is no other cost, your beginning point (y-intercept) is zero.   Write the linear equation y = mx + b for the total cost of x loaves of bread.

y = 2.50x

To write the linear equation for the total cost of x loaves of bread, we need to use the formula y = mx + b, where y represents the total cost and x represents the number of loaves of bread.

In this case, the rate (m) for a loaf of bread is $2.50. Since there is no other cost (b = 0), the equation becomes:

y = 2.50x + 0

Simplifying, we get:

y = 2.50x

Therefore, the linear equation for the total cost of x loaves of bread is y = 2.50x.