[(20+339:3+a)×7-5×400]:3-22×3+125×8=1000
[(20+113+a)×7-2000]:3-66+1000=1000
[(133+a)×7-2000]:3-66=1000-1000
[(133+a)×7-2000]:3-66=0
[(133+a)×7-2000]:3=0+66
[(133+a)×7-2000]:3=66
(133+a)×7-2000=66*3
(133+a)×7-2000=198
(133+a)×7=198+2000
(133+a)×7=2198
133+a=2198:7
133+a=314
a=314-133
a=181
