If I’m not mistaking there’s 4, In other words two eighth rests make up a quarter rest, while four of them make up a half rest, and eight 1/8 notes make up a whole rest.
That big triangle is made up of 2 congruent 30-60-90 triangles with each base measuring 4.5. You could use the tangent ratio to get tan60 = x / 4.5. Multiply both sides by 4.5 to get 4.5 tan60 = x. Do that on your calculator in degree mode to get that x = 7.79 or 7.8
