(38a + 120) : 25 × 54 = 100 + 980
(38a+ 120) : 25 × 54 = 1080
(38a + 120 ) : 25 = 1080 : 54
(38a + 120) : 25 = 20
38a + 120 = 20 × 25
38a + 120 = 500
38a = 500 - 120
38a = 380
a = 380 : 38
a = 10
7777 - (11 + a - 1111+ 777) × 7 = 777
7777 - ( 11 + a - 1888) = 777: 7
7777 - (11 + a - 1888) = 111
11 + a - 1888 = 7777 - 111
11 + a - 1888 = 7666
11 + a = 7666 + 1888
11 + a = 9554
a = 9554 - 11
a = 9543
la a treia nu stiu, scuze
