What is the measure of angle TQR?

Angle TQR equals to 70 degrees

First you have to find the value of x. An inscribed quadrilateral in a circle has it that opposite angles are supplementary.

So set the angles STQ and SRQ to 180.

3x+5+5x+15=180
8x+20=180
8x=160
x=20

Then find the angles of the three by substituting 20 as x.

Angle STQ=65
3(20)+5
60+5
65

Angle RST=110
4(20)+30
80+30
110

Angle SRQ=115
5(20)+15
100+15
115

Exterior angles of a quadrilateral equal to 360 when added together. So subtract the values from 360 to get the missing length.

360-115-110-65=70

So angle TQR=70