I'am having a hard time sovling math problems or any thing realted to math even in easy problems how can i improve my self , is there any websites that i can use to learn math , solving math problems is not helping me since i cant even understand the solution , how can i come up with solution to math problems , for example in this problem 1985G - D-Function like how can people come with the solution that say to satisfy the equation all digits should be less than or equal to k/9 ? how do i even come up with this, i hope someone can help.