a, 426 x X + 74 x X = 229000
=> X x ( 426 + 74 ) = 229000
=> X x 500 = 229000
=> X = 229000 : 500
=> x = 458
b, X x 99 + X = 23400
=> X x ( 99 + 1 ) = 23400
=> X x 100 = 23400
=> X = 23400 : 100
=> X = 234
c, X x ( 143 - 133 ) = 1440
=> X x 10 = 1440
=> X = 1440 : 10
=> x = 144
d, X + 281 + 716 = 209 x 43
=> X + 997 = 8987
=> X = 8987 - 997
=> X = 7990