Question 1042339
a) The total cost for Amanda if she buys from KitchenPlus is 0.90(550 + 14.50x).  Her average cost per tile is thus {{{(   0.90(550 + 14.50x) )/x}}}.


b)  To determine how many tiles Amanda has to order for the average cost per tile to be equal at both TileAll and KitchenPlus, solve the equation 

{{{( 0.90(550 + 14.50x) )/x = (378 + 15x)/x}}}.  (Assuming {{{x<>0}}}.)

===> 495 + 13.05x = 378 + 15x

===> 117 = 1.95x   ===> x = 60 tiles.