To find the perimeter of a triangle we have to add the lengths of all the sides.
Perimeter = (10b+3c)+ (4b+4d) + (5d+7c)
Simplify by combining like terms
10b+3c+4b+4d+5d+7c
10b+4b+4d+5d+3c+7c
14b+9d+10c
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