Simple....
you have:

You're trying to find b..so isolate it...

leaving you
a=c*b
still not done....


Thus, your answer.
20 would be the common denominator and the answer would be 12/20 and 15/20
Answer:
The last one: deciliters to hectoliters.
Step-by-step explanation:
Step-by-step explanation:
Step 1:
A . 5 with an exponent of 3 times 5 with an exponent of -4
=
=
=
= 1/5
B . (1/4) with an exponent of 3 times (1/4) with an exponent of 2
=
C. Same as above
D. 
Step 2 :
All the above expressions have a value between 1 and 2