There are some birds in 2 trees. 3/7 of the birds are in the 1st tree and the rest are in the 2nd tree. 52 birds fly away from the 1st tree. 1/4 of the birds fly away from the 2nd tree. There are now 2/3 of the birds left in total. How many birds were in the 2nd tree at the start?
If there were x birds, then we have
3/7 x - 52 + 3/4 * 4/7 x = 2/3 x
x = 273
now finish it off