Suppose Xiaoming's parents spent X yuan on education savings, and the interest for six years is: 6*2.88%*x =0. 1728x yuan.

When Xiaoming went to college, the sum of principal and interest was (1+6*2.88%)*x yuan.

Re-loan: 20000-(1+6 * 2.88%) * x = 20000-1.1728x,

The loan interest is: [20000-(1+6 * 2.88%) * x] *10 * 6.21%/2 = 6210-0.3642x,

The equation can be listed from the meaning of the question: 0.1728x = 6210-0.3642x,

Solution: x= 1 1550 (about),

20000-1.1728x = 6450 (approximate value). )

So Xiaoming's parents spent 1 1550 yuan to participate in education savings.

When Xiao Ming went to college, he borrowed another 6450 yuan.