Hi Anonymous 4338,
thanks to answering questions today.
That one, d=56m
it didn't occur to me that this was a side of length of 56m, but I think you hit the meaning right on the head and that's Excellent!
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Now, let's look at your question.
8.1(z+2.3) = 4.9(z-4.2)
first expand th brackets on both sides
8.1z + 8.1*2.3 = 4.9z - 4.9*4.2
8.1z + 18.63 = 4.9z - 20.58
now you need to get all the lots of z on one side and all then numbers without zs on the other side
start by subtracting 18.63 from both sides (whatever you do to one side you have to do to the other side as well)
8.1z + 18.63 - 18.63 = 4.9z - 20.58 - 18.63
8.1z = 4.9z - 39.21
Now subtract 4.9z from both sides
8.1z - 4.9z = 4.9z - 39.61 - 4.9z
(8.1 - 4.9)z = -39.21
3.2z = -39.21
now you just need to get rid of 3.2 the opposite of times 3.2 is divide by 3.2
3.2z / 3.2 = -39.21 / 3.2
z = -12.253125
z = -12.25 (correct to 2 decimal places or correct to 4 significant figures)
There you go. That's how it is done.
+118687 
