Respuesta :

Answer:

14

Step-by-step explanation:

Since S is the midpoint of RT, then RS = ST

RS = RT - ST = (3x + 7) - (x + 7) = 3x + 7 - x - 7 = 2x

so we get that RS = 2x

but since RS = ST, and RS=2x & ST=x+7

then 2x = x + 7

       2x-x = 7

        x = 7

ST = x+7 = 7+7 = 14

P.S. Hope it makes sense. If you have any questions, feel free to ask them in the comments senction. I'll be happy to help. Have a wonderful day!