a+b=380
a-b=3×b/a=3×b+b=4×b
4×b+b=380
5b=380
b=380:5=76
a+76=380
a=380-76=304
2)a+b+c=246
a/....../
b/....../......../ b=2×a
c/....../........./+36/ c=2×a+36
a+2×a+2×a+36=246
5×a=246-36
5×a=210
a=42》b=42×2=84》c=84+36=120
3)M+A+C=91
A=M:2
C=A:2
M/...../...../..../...../
A/..../..../
C/.../
C+C×2+C×4=91
C×7=91
C=91:7=13
A=13×2=26
M=13×4=52
4)A=3×B
C=3+B
A-B=14
A/......./......./......./
B/......./
C/....../+3
A-B=14》2×B=14 》B=7
A=7×3=21
C=7+3=10