Let a produce a number and b produce a number.

A=(B+396)/3

B=(A+396)/4

Replace B=(A+396)/4 with A=(B+396)/3.

B=[(B+396)/3+396]/4

4B=B/3+ 132+396

1 1B= 1584

B= 144

So A=( 144+396)/3.

A= 180

Total = a+b+396 =180+144+396 = 720.

3。

set up

alcohol concentration

X%

300*X%+70%*500=55%*(300+500)

300X+35000=44000

X=30

The alcohol concentration is 30%