If $a+b=5$ and $3 a+2 b=20$, then $(3 a+b)$ will be:
(a)10
(b)15
(c)20
(d)25
Answer
Answer (as printed): D
Explanation
$a+b=5$ Multiplying (i) by 2 and subtracting from (ii), we get: $a=10$. Putting $a=10$ in (i), we get: $b=-5$. $$\therefore \quad(3 a+b)=3 \times 10+(-5)=30-5=25 .$$
Explanation as extracted from the printed page; notation may be imperfect.