Could someone help me with these??

The angle of a triangle are given as 6x,(x-3), and (3x+7). find x then find the measures of the angles

Suppose a laboratory has a 30 g sample of polonium-210. the half-life of polonium-210 is about 138 days how many half-lives of polonium-210 occur in 1104 days? how much polonium is in the sample 1104 days later? 9; 0.06 g 8; 0.12 g 8; 2,070 g

Five infinity stones cost $16.80. what is the price per infinity stone ?