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.