Question

The problem below has been solved incorrectly. Identify and explain the error.

Answer 1

Answer:

If you look over the steps you can see that until 4x + x + 3 = 18, evertything is dandy. But the step after that 4x + x =21 seems a bit fishy.

Think about it they subtract 3 from both sides so the first side is correct

4x + x, but they added 3 to the other side:

$(4x+x+3) - 3 = 18 - 3\\4x+x = 15$

not

4x+x = 21

Then we solve for 4x + x = 15

$5x = 15\\x = \frac{15}{5} \\x = 3$

To solve for y we use :

y = x+3

y = 3+3 = 6

so (3,6) is the right answer