Verified answer

a rectangle with sides a and b has a perimeter of 2a+2b

your triangle has a perimeter of:

2(3x-4)+2(7x+10)=6x-8+14x+20=20x+12

Let length be a and breadth b,

The formula for perimeter is the sum of all the sides

= a + b + a + b

= 2(a + b)

In this case, a = 7x + 10

b = 3x - 4

Perimeter:

2(7x + 10 + 3x - 4)

= 2(10x + 6)

= 20x + 12

The perimeter is 20x + 12 units

Perimeter formula

P = 2L + 2W

p = 2(7x + 10) + 2(3x - 4)

P = 14x + 20 + 6x - 8

P = 20x + 12

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Double both expressions

Add

Get 20x + 12

20x+12=perimeter

because..3x-4+3x-4+7x+10+7x+10=20x+12