3*( 1+x)^3=5

x=0. 18563 1

rule

Sum of the present value of investment in 6 yuan at the end of the first month, the second month, the fourth month and the sixth month:

s 1 = 6 *( 1+0. 18563 1)= 7. 1 14

s2=6*( 1+0. 18563 1)^2=8.434

s4=6*( 1+0. 18563 1)^4= 1 1.856

s6=6*( 1+0. 18563 1)^6= 16.667