It is because a triangle has 2 sides and the question shows that 2 triangles equal the same so that becomes 2x. The third side is 4 so u add that to 2x which becomes 2x+4 and the perimeter equals 49 so basically the equation should be </span>2x + 4 = 49.
<u>ANOTHER EXPLANATION: </u>The equation for perimeter is P=L+W SO SUBSTITUTE ALL THE NUMBERS THAT ARE INCLUDED IN THE QUESTION AND THEN U CAN GET UR ANSWER.
