This is an equilateral triangle because all the sides are the same length shown by the tic marks. This means that the angles are also all congruent. so... S=T=R this also means that all angles are 60 degrees because all triangles angles added together are 180 degrees. so that means that you put all of the equations equal to 60. but if u are looking for x only here is the answer 7x+4=60 7x=56 x=8
