The correct answer is A. D
That is because D has a horizontal line of symmetry, as can be seen on it.
This is how I'd solve it:
bench = x x+3x=600
table = 3x 4x=600
x=150
The bench costs <u>$150</u> and the table costs <u>$450</u>; combined, they cost $600, so it's correct. I hope this helps you!