„Ms. Karone orders a total of 350 black, blue, and red pens for the school.
• She orders 170 black pens.
• She orders 120 blue pens.
Which equation can be used to find r, the number of red pens Ms. Karone
orders?
350 - 170 – 120 =r
350 + 170 + 120 =
350 – 170 + 120 = r.
350 +170 – 120 = r