Explanation:
451₆ - P₇ = 305₆
P₇ = 451₆ - 305₆
P₇ = 142₆
convert 142₆ = 1 * 6² + 4 * 6¹ + 2 * 6⁰
= 36 + 24 + 2
= 62
Convert 62₁₀ to base 7
62/7 = 8 R 6
8/7 = 1 R 1
1/7 = 0 R 1
∴P₇ = 116₇