Question

what is the value of a in the equation 5a - 10b = 45, when b = 3?
○ 3
○ 15
○ 21
○ 39

Explanation:

Step1: Substitute \( b = 3 \) into the equation

We have the equation \( 5a - 10b = 45 \). Substitute \( b = 3 \) into it: \( 5a - 10\times3 = 45 \).

Step2: Simplify the equation

Calculate \( 10\times3 = 30 \), so the equation becomes \( 5a - 30 = 45 \). Then add 30 to both sides: \( 5a = 45 + 30 \), which simplifies to \( 5a = 75 \).

Step3: Solve for \( a \)

Divide both sides of \( 5a = 75 \) by 5: \( a=\frac{75}{5}=15 \).

Answer:

15 (The option corresponding to 15, e.g., if the option is labeled as "15", then the answer is the option with 15. Based on the given options, it's the second option: 15)