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