Hey friend in order to figure that out, we need to solve all of these proportions.
Lets start with A!
What you first want to do is cross multiply so...
10 * 100 = 25 * 40
Simplify
1000 = 25 * 40
1000 = 1000
Add -1000 to both sides
1000 - 1000 = 1000 - 1000
0 = 0. (This proportion is true)
Moving on to B
Same steps!
18 * 50 = 48 * 20
900 = 48 * 20
900 = 960 (This is false therefore B is our answer however we want to check the others as well)
C is...
25 * 135 = 45 * 75
3375 = 45 * 75
3375 = 3375
3375 - 3375 = 3375 - 3375
0 = 0 (True)
D is....
24 * 25 = 30 * 20
600 = 30 * 20
600 = 600
600 - 600 = 600 - 600
0 = 0 (True)
