[tex] {\qquad\qquad\huge\underline{{\sf Answer}}} [/tex]
Let's solve ~
[tex]\qquad \sf \dashrightarrow \: 10x + 30 = 90[/tex]
[ according to given figure ]
[tex]\qquad \sf \dashrightarrow \: 10x = 90 - 30[/tex]
[tex]\qquad \sf \dashrightarrow \: 10x = 60[/tex]
[tex]\qquad \sf \dashrightarrow \: x = 60 \div 10[/tex]
[tex]\qquad \sf \dashrightarrow \: x = 6 \degree[/tex]
Correct choice is D
