If $4a + b = 3$ then $20a + 5b =$? Is this solvable? I think not, I think something is missing.
Am i wrong?
If 4a + b = 3 then 20a + 5 = ?
a. 15
b. 1/4
c. 4/3
d. 3/4


You are quite correct: something has to be missing. No matter what value you give $a$, there is a value of $b$ that makes the first equation true, so $20a+5$ is indeterminate. 
From the answers given, it’s clear that the second expression was supposed to be $20a+5b$; since this is $5(4a+b)$, the intended correct answer must be $15$.
