Seven nuts and eight bolts weigh 326 grams. Eleven nuts and ten bolts weigh 448 grams. Find the weight of 12 nuts and 12 bolts.

Let the weight of one nut = x gm

weight of one bolt = y gm

Now according to the conditions

7x + 8 y = 326 gm  ..... (1)

11x + 10 y = 448 gm  ..... (2)

solving (1) and (2) we get 

x= 18 gm  and y = 25 gm

therefore weight of 12 nuts = 12 * 18= 216 gm

and weight of 12 bolts= 12 * 25= 300 gm