b, e, and c
this is how you can tell
b: 7/2, both the top and bottom × 3 will get 21/6, 7×3=21, 2×3=6 so they are proportional
e: both 5 and 2 multiply 5: 5×5=25, 2×5=10, so 25/10 is proportional to 5/2
c 4×3=12, 5×3=15
the others are not.
another way to do it is what I call 'diagonal times'. for example;
, you multiply diagonally, 5×11=55, 6×9=54, 55 and 54 are not equal, so they two fractions are not proportional.
try this "diagonal times" on b, c, e, you'll see you get two products that are equal.