The equation is 2(10+x)=28 where x is the unknown number we are trying to find. Use distrubutive property to combine like terms. 2 times 10 is 20 and 2 times x is 2x. Now we have 20+2x = 28. What you do to one side you must do to the other. 20 minus 20 is 0. 28 minus 20 is 8. Now our equation is 2x is 8. To find 1 x we divided in half. 8/2 is 4 therefore the missing variable is 4.
