Which expression is equivalent?​

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

Given that ot =5, xt=12, and ox= 13 is xy tangent to circle o at t? explain.

Noor brought 21 sheets of stickers. she gave 1/3 of a sheet to each of the 45 students at recess. she wants to give teachers 1 1/2 sheets each.