A grower planned to plant 160 trees in an orchard. He planted n equal rows. Write down an expression for the number of trees in each row. He noticed that if he had ten more trees he could have planted two more rows, but with three trees fewer in each row. Write down an equation involving n. Show that the equation can be rewritten as: 3n^2 +16n -320 = 0 Then solve this equation and hence find the number of rows he actually planted.