How to do the 16th question
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Explanation:
Set up 2 equations using what you know.
(1) x - y = 3
(2)
x
2
−
y
2
= 69
Now solve them simultaneously through substitution.
Using the (1), x = y + 3
Substituting this x value into (2)
(
y
+
3
)
2
-
y
2
= 69
y
2
+
6
y
+
9
−
y
2
= 69
y
2
cancels out.
6
y
+
9
= 69
6y = 60
y = 10
Now subbing y into (1)
x - 10 = 3
x = 13