Question

6.03] The three Math Idol judges have been eliminating contestants all day! The number of one-step equations and two-step equations who have been eliminated today is equal to 840! If three times the number of one-step equations minus twice the number of two-step equations is equal to 870, how many one-step equations auditioned today?

330

510

520

660

Answer 1

...x - 1-step
y - 2-step

x + y = 840
3x - 2y = 870

--Use substitution--
3(840 - y) - 2y = 870
--Solve for y--
y = 330
--plug y in the first equation--
x + 330 = 840
--solve for x--
x = 510