Answer:
(1)..................let no. be x and y
x+ y= 16
x-y= 3
adding both eqn= x+y+x-y=16+3
2x=19
x= 19/2
now..19/2+y=16
y=16-19/2= 13/2
(2).....let red balls weight = x...blue balls weight= y
3x+2y=66g....bag 1
x+4y=72g....bag 2
by egn 2...x= 72-4y
puuting x value in eqn 1= 3(72-4y)+2y=66
216-12y+2y=66
y= 15 g...weight of a blue ball
now...x= 72-4y
x=72-4×15=12g...weight of a red ball