Answer: 12 = x + 4
Explanation:
We know that the length of the green line is 12.
And the length of the black line will be equal to the sum of the lengths of the two smaller segments, x, and 4
Then the length of the black line is x + 4
We want to write an equation that says that the length of the green line is equal to the length of the black line, this is:
Length of green line = Length of black line
12 = x + 4
That is the equation we wanted.
Now we could solve it if we subtract 4 in both sides of the equation:
12 - 4 = (x + 4) - 4
8 = x