Respuesta :

0.50x+25 would be the expression form of the situation
Think:  slope-intercept form of the equation of a straight line:  y=mx+b.
Here the "flat rate" of $25 is "b" and the "slope" of the line is $0.50/mile.

Thus, the correct algebraic expression is 

y=($0.50/mile) + $25.