R = red beads
G = green beads
B = blue beads
Given:
R/2 = G/3 = B/7
B = R + 150
How many reds?
R/2 = (R+150)/7
7*R/2 = R + 150
7*R = 2*R + 300
5*R = 300
R = 60
How many blue?
B = R + 150
B = 210
How many green?
G/3 = R/2
G/3 = 60/2
G/3 = 30
G = 90
How many total?
Total = R+G+B
Total = 60+90+210
Total = 360