Question

I've been trying to figure this out for 1 Hour

Answer 1

For both terms of the equation 21d + 18 we can factor 3, like this:

21d + 18 = 3×7d + 3×6

Then, we get:

3×7d + 3×6 = 3×(7d + 6)

Then, the equation 3(7d + 6) is equivalent to 21d + 18