what is the value of a in the equation 5a - 10b = 45, when b = 3?\n3\n15\n21\n39

Answer:

C. 21

Explanation:

Step1: Substitute b value

Substitute (b = 3) into (5a-10b = 45), we get (5a-10\times3 = 45), which simplifies to (5a - 30=45).

Step2: Isolate the term with a

Add 30 to both sides of the equation: (5a-30 + 30=45 + 30), so (5a=75).

Step3: Solve for a

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