Answer:
y=x+5
Explanation:
You can tell by looking at the sequence that each number is five more than the previous. With that in mind, you know that, to find the next number in the sequence, you have to add five to the one before it.
Making x the previous number and y the next number in the sequence, you get the equation y=x+5
You can plug pairs from the sequence to check:
2= -3+5
2=2
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7= 2+5
7=7
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12= 7+5
12=12