first you open up the brackets so the sign for 2d changes to positive. So it will look like 3d-9+2d=51 then u simply the 3d-9+2d that should give 5d-9=51. Then you add 9 to both sides of the expression 5d-9+9=51+9. That will be 5d =60 so you divide 5 on both sides to find the value of 1 d which is 60/5=12 then to find 3d you multiply the value of d by three so it's 12(3)=36
