Answer:
7
Step-by-step explanation:
Q R
T S
I put the letters here in order, a clockwise order starting at Q.
If you look at our diagram you will see that RT and QS are actually the diagonals of this rectangle.
The diagonals of a rectangle are congruent.
We have the measurement of RT = the measurement of QS.
That is we have this equation: 4x-16=x+5.
4x-16=x+5
Subtract x on both sides:
3x-16= 5
Add 16 on both sides.
3x = 21
Divide both sides by 3.
x = 7
