The 15 lbs at $7=$105
So multiple 5x9 as a test and check results. 105-45=60
Here you can see that 60 is a factor of 6 by 10 so you got lucky and got the answer of 10lbs at $6 & 5lbs at $9=15 lbs at $7 average
AC = x, CD = 2x cause of 30° angle. Use pythagoras then
AB is 6 because you just subtract BC from AC to find the other missing length.