Let the cost of a audio cassette be Rs x and that of a video cassette be. Rs y Then,

Multiplying equation (i) by 4 and equation (ii) by 3, we get

Substituting equation (iv) from equation (iii), we get

Substituting 30 x 30 in equation (i), w get

Hence, cost of one audio cassette = Rs30 and cost of one video cassette = Rs300