设甲种存款有x万元,则乙种存款有5-x万元,
x*3.1% + (5-x)*3.5% = 0.163
3.1x + 17.5 - 3.5x = 16.3
0.4x = 1.2
x=3
甲种存款有3万元,乙种存款有2万元.