Answer:
missing length = 6x - 5
Explanation:
the perimeter is the sum of the 3 sides.
subtract the sum of the 2 given sides from the perimeter for missing side, that is
10x - 6 - (x + 1 + 3x - 2)
= 10x - 6 - (4x - 1 ) ← distribute parenthesis by - 1
= 10x - 6 - 4x + 1 ← collect like terms
= 6x - 5
missing length = 6x - 5