Respuesta :

Let x = the next score

If    (81 + 89 + 90 + 83 + 77 + x)  ÷  6 = 82

  ⇒  420 + x = (82 × 6)

  ⇒  x = 492 - 420
     
       x = 72

Thus to get an 82 average he need to get 72 on his next test.