In math if you are working with algebra and you see a number that automatically means a variable, like x for instance. Now they're telling you to double the number (x). This means you must multiply by two. Finally they tell you to add by 4. Now you have your expression. But now they're asking you for x to be 3 as the number you were thinking of. Just plug it in and use order of operations (mutiplication first then add), so do 3 times 2 you get 6 then add 4 and get 10. Hope I helped!!!
