Can someone help me with this it's due today​

37 centimeters

Step-by-step explanation:

First, since the triangles are similar, find out how much larger STR is than HIJ by finding an similar side and dividing the numbers. Since the only similar side that we know both numbers on it ST and HI, so we divide 10 by 4 to get the unit rate, which is 5/2. The missing side on STR is the bottom, so to get it, multiply 6, the bottom of the other triangle, by the unit rate, 5/2, to get the answer of 15. Then, perimeter is all of the sides added up, so 10+12+15=37 cm.

(hope this helps :P)