Respuesta :
remmeber you can do anything to an equaiton as long as you do it ot both sides
isolate placeholder
7x+21=105
subtract 21
7x+21-21=105-21
7x+0=84
7x=84
divide both sides by 7
7x/7=84/7
x=12
isolate placeholder
7x+21=105
subtract 21
7x+21-21=105-21
7x+0=84
7x=84
divide both sides by 7
7x/7=84/7
x=12
x = 12 all you have to do is subtract 21 from 105 your answer would be 84 then you would do 84 divided by 7 and the answer would be 12 so x equals 12