You cross multiple to get the same denominator so you can properly divide the fraction
My calculator shows that
(2.1)/(1.488) = 1.41129
which is approximate. If you want the result to two decimal places, then it would be 1.41 and not 1.40
Try 1.41 and it should work out, assuming your teacher wants two decimal places.
I think the answer is D because you have to move the decimal three times anyway, then you only need to add seven more zeroes to make it correct (in my opinion).
The answer for this question is 0.55%
A: cost= 3*55+.35m
B: cost=3*50+.40m
set the costs equal, and solve for m.