HELP!!! (方程)complete There have two questions

1)
A+B+C =405
A=4B
C=A+45
4B+B+(A+45)=405
4B+B+(4B+45)=405
5B+4B+45=405
9B=405-45
9B=360
B=40
A=4B=4*40=160
C=A+45=160+45=205
Final check
A+B+C=160+40+205=405 (GOOD!)
2)
Let x be the no. of elderly monks.
So, the no. of younger monks is (100-x).
100buns were distributed with elderly monks got 3buns per head and 3 young monks had to share 1 bun.
100 = 3x + (100-x)/3 * 1
100 = 3x + (100-x)/3
100*3 = 3x * 3 + (100-x)/3*3
300 = 9x + 100 - x
200 = 8x
x=200/8=25
So, there are 25 elderly monks and (100-25)=75young monks.

1)
A+B+C=405
A=4B
C=A+45
then:
4B+B+4B+45=405
9B=360
B=40

A=160
C=205

2)Let there are a elderly monks and b young monks, x be get the numbers of buns
then
a=3x
3b=x

3x+x=100
x=25

so a=75
b=25

because every elderly monk can get three buns, so 75/3=25 elderly monks
every three young monks share one bun, so 25*3=75 young monks


hope this can help you to solve your problem