Answer:
n = 4
Step-by-step explanation:
3ⁿ⁺¹ - 3ⁿ⁻¹ = 216 Separate exponents
3ⁿ×3¹ - 3ⁿ×3⁻¹ = 216 Factor
3ⁿ(3 – ⅓) = 216
3ⁿ(8/3) = 216 Multiply each side by 3/8
3ⁿ = 81 Factor 81
3ⁿ = 3⁴ Compare exponents
n = 4
=====
Check:
3⁵ - 3³ = 216
243 – 27 = 216
216 = 216
