Hey there!
The value of "n" is 10.
Since the lines on the sides represent congruency of those 2 sides, we also know that angle T is equal to angle S. Since a triangle's angles add up to 180°, we can use the following equation, and solve:
180 = 3.5n + 3.5n + 11n Add the "n"s
180 = 18n Divide both sides by 18
10 = n
Hope this helps! Good luck on your assignment! Have a great day!