so it gives you the "= 210" part of it so you just need to figure out how to write "40% of a number is added to the number"
the questions already tells you that "the number" is "x"
so that means "40% of x is added to x"
instead of writing "add" you can replace it with a plus sign "+"
(40% of x) + x
another way to write 40% of x is 0.40x
so your equation is .4x + x = 210
