When you're comparing two numbers like this, you're really looking at how the two are related.

"The sum of -4 and 5 times a number is multiplied by 3."

This means that -4 is added to 5X (five times a number). Then that quantity is multiplied by three.

3(-4 + 5x)

The sum of that is equal to seven times that same X (7x) plus 212.

So,

3(-4+5x) = 7x + 212

Distribute the 3 through the parenthesis:

-12 + 15 x = 7x + 212

Isolate all the x-terms on one side by first subtracting the 7x from both sides.

-12 + 15x - 7x = 7x -7x +212

Simplify

-12 + 8x = 212

Now isolate the terms without variables on the right by adding 12 to both sides

-12 + 12 + 8x = 212 + 12

Simplify

8x = 224

Divide both sides by 8 to isolate x

8x/8 = 224/8

x = 28