answer: [tex]d = 12[/tex]
explanation:
[tex]6(d+1) - 2d=54[/tex] | multiply the 6 into the parentheses
[tex]6d + 6 - 2d = 54[/tex] | add the 6d and -2d, bc they are like terms
[tex]4d + 6 = 54[/tex] | subtract 6 and move it over to 54
[tex]4d = 48[/tex] | divide by 4
[tex]d = 12[/tex] | final answer
hope this helps! ❤from peachimin
