3s-3t=4 ②
①-② 5t=3,
The solution is t=3/5,
Substitute (1)
3s+6/5=7
The solution is s=29/ 15.
∴s=29/ 15,
t=6/5
m/3-n/4=- 1 ①
m/2+n/3=7 ②
① 4m-3n of * 12 =- 12 ③
② 3m+2n=42 ④ for * 6
③*2+④*3 is 17m= 102.
The solution is m=6, and it is substituted into ③.
24-3n=- 12
The solution is n= 12.
∴m=6
n= 12