a, 1855 : x = 1824 - 1789
=> 1855 : x = 35
=> x = 1855 : 35
=> x = 53
b, x : 122 + 63406 = 85742
=> x : 122 = 85742 - 63406
=> x : 122 = 22336
=> x = 22336 x 122
=> x = 2724992
c, \(x\times24+8789=11285\)
\(\Rightarrow x\times24=11285-8789=2496\)
\(\Rightarrow x=2496:24\)
\(\Rightarrow x=104\)
d, x : 105 + 67506 = 75742
=> x : 105 = 75742 - 67506
=> x : 105 = 8236
=> x = 8236 x 105 = 864780