Answer: X = y - yi - 7i
Y = (x + 7i)/(1 - i)
Step-by-step explanation: for the case of (X) you only need to pass the 7i to the other side with the subtraction sign (-7i), then we get this equation:
x + 7i = y − yi
X = y - yi - 7i
in the case of the (Y), first we select the common multiple.
y - yi = y(1 - i)
if we replace it in the original expression, we get the following equation:
x + 7i = y(1 - i)
after that you can pass the value (1 - i) to the other side dividing,
Y = (x + 7i)/(1 - i)
AS we know that:

And we have the volume and we can calculate the SA,,,
So that, we can conclude:

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The answer is probably 50 ok