To answer the question, let the number of nickels Peggy has be n. By this, the Peggy has 3n quarters. The total amount of all his nickels and quarter is equal to $1.60. The equation that best describe the situation is,
25(3n) + 5(n) = 160
Simplification leads to,
75n + 5n = 160
Thus, the answer is letter D.