52-(7x-x/3)*2=12
52-14x-2x/3=12
14x-2x/3=40
40/3x=40
x=3
验算给你看:
52-(7*x-x/1/3)*2
52-(7*3-3/1/3)*2
52-(21-1)*2
52-20*2
52-40
12