The answer for the first box is 90
Why? Because this is from the expression 90x+1500. The 90x means the slope is 90. So each time x goes up by 1, the value of y goes up by 90
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The answer to the second box is 1500
If you were to plug in x = 0, then
y = 90x+1500
y = 90*0+1500
y = 1500
So he earns $1500 for selling 0 copies