you have to read the bottom link for the answer key
Yes it is linear
It is a negative slope
I am attaching pic of graph
The slope is -3/4
Y intercept is (0,2)
3x : 2 = 15
3x = 15 * 2
3x = 30
x = 30 : 3
x = 10
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3(10) :2 = 15