According to the conditions in the title, two equations are listed: Xiaoming and Xiaoxi * * * have 20 sugars: x+y=20 Xiaoming has 4 more sugars than Xiaoxi: x=y+4. Solve this set of equations and get the candy numbers of Xiao Ming and Xiao Xi respectively. Substitute X in Equation 2 into Equation 1: (y+4)+y=20, 2y+4=20, 2y= 16, y=8, and substitute y=8 into Equation 2 to get the number of sweets for Xiaoming: x=8+4, x = 65438+.

Algebraic problem solving is one of the commonly used problem solving methods in mathematics, which is suitable for all kinds of practical situations and mathematical problems. The equations are established, the problem is transformed into a mathematical expression, and the unknown value is solved by mathematical operation to get the solution of the problem. Algebraic problem-solving is widely used in mathematics education to cultivate students' logical thinking and problem-solving ability.