(4-2b)/3-1/2=1/6
2(4-2b)-3=1
8-4b=4
b=1
( x-7)/2=-4/3+1/2
3(x-7) = 2(-4)+3
3x-21 = -5
3x = 16
x = 16/3
設該兩位數的個位數字x,十位數字為y
{ x-y=3 ...(1)
10y+x+10x+y=121 ...(2)
由(1), x-y=3
x=y+3 ....(3)
把(3)代入(2)
10y+y+3+10(y+3)+y=121
22y+33=121
y=4
把y=4代入 (3), x=4+3
x=7
該兩位數為 47