Determine whether the equation 6x^2+y=4 is a linear

Each month, a shopkeeper spends 5x + 14 dollars on rent and electricity. if he spends 3x−5 dollars on rent, how much does he spend on electricity? for which value(s) of x is the amount the shopkeeper spends on electricity less than $100? explain how you found the value(s).

Need 50 will mark brainliest answer. find the lengths of all the sides and the measures of the angles.

The anwser cause i do not understand just plez