Question 202251
(1) 100=4C +12B,,,(divide by 4),,,25=1C+3B,,(25-3B) = C
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(2) 100=10C+5B,,,(divide  by 5),,,20=2C+1B
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subst  (1)  in  (2)
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20 =2(25-3B) +B
20 = 50 -6B+B
-30= -5B
6=B
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from  (1) C=25-3B
C=25-3(6)
C=7
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check
(1) 100=4(7)+12(6)= 28+72 = 100,,,,ok
(2) 100 =10(7) +5(6) = 70+30=100,,,ok