∠1 and ∠2 are complementary.

∠1=x°∠2=(3x+30)°

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what is the value of x? .

If angles are complementary, they add up to 90 whereas when they are supplementary, the add up to 180. So now let's focus on this problem. It says angle 1 and 2 are complementary. Therefore;
angle 1 + angle 2 =90
x+(3x+30)=90
x+3x+30=90
4x+30=90
-30 -30
4x=60
4/4x=60/4
x=15
Therefore, the value of x is 15