Answer:
At 15 weeks they will both weigh 180 
Explanation:
150 + 2w = 195 - w 
2w + w = 195 - 150 
3w = 45 
w = 45/3 
w = 15 <=== they will weigh the same at 15 weeks 
 
150 + 2(15) = 150 + 30 = 180...and they will both weigh 180 lbs 
I hope this helps you :)