If 3d - (9 - 2d) = 51, find the value of 3d.

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

3d - (9-2d) = 51

= 3d-9+2d = 51

=5d-9 = 51

= 5d=60

d=60/5 = 12

so 3d = 3*12 = 36