Question

1. if $3a+4b = 4a-4b = 21$, find the value of $a$.

a. 3
b. 6
c. 21
d. 42

Explanation:

Step1: Set up equations from given equality

We have two equations:
$3a + 4b = 21$
$4a - 4b = 21$

Step2: Add the two equations

Adding eliminates $4b$ and $-4b$:
$$(3a + 4b) + (4a - 4b) = 21 + 21$$
$$7a = 42$$

Step3: Solve for $a$

Divide both sides by 7:
$$a = \frac{42}{7}$$

Answer:

B. 6