Which of the following proportions is false? 10/25=40/100 18/48=20/50 25/45=75/135 24/30=20/25

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)

Many things that seem threatening in the dark become welcoming when we shine light on them