The first step to solving this equation is to do the necessary mathematics to isolate the dd terms on one side of the equation and the constants on the other side of the equation while keeping the equation balanced:
color(red)(16d) - 16d + 4 = color(red)(16d) + d16d−16d+4=16d+d
(color(red)(16d) - 16d) + 4 = color(red)(16d) + d(16d−16d)+4=16d+d
0 + 4 = 16d + d0+4=16d+d
4 = 16d + d4=16d+d
Next, we can combine like terms:
Hint: remember (color(green)(k = 1k)k=1k)
4 = (16 + 1)d4=(16+1)d
4 = 17d4=17d
Now, we can solve for dd while keeping the equation balanced:
4/color(red)(17) = (17d)/color(red)(17)417=17d17
4/17 = (color(red)(cancel(color(black)(17)))d)/color(red)(cancel(color(black)(17)))
4/17 = d or d = 4/17
