Triangle Symbol Equation — Find the Number

A triangle symbol stands for a mystery number. The equation 67 − ▲ = 32 + 17 looks tricky because of the symbol, but once you see it as a plain subtraction equation the answer comes in two steps: add the right side first, then find what was subtracted from 67.

Symbol-for-number equations (▲, ★, □) appear regularly in the very easy to easy band of OC MR. They are designed to check whether students can treat an unfamiliar symbol exactly like a variable. The most common mistake is trying to guess from the answer options instead of solving the right side first.

The examiner is checking whether students can simplify the right-hand side before solving, rather than trying all five options. Distractor D (49) is the value of the right side — students who forget to subtract it from 67 pick D instead of B.

A symbol (triangle, star, square) represents an unknown number. A simple one-step equation is given with arithmetic on one or both sides. Students must evaluate both sides and isolate the symbol. The distractors include the right-side total, one of the numbers in the equation, and values that result from common arithmetic errors.