\(a)\\y=3x+12\\\\the\ slope:m=3\\\\y-intercept:(0;\ 12)\\------------------\\\\b)\ x=7\\\\the\ slope-unde fined\\\\y-intercept-not\ exist.\)
\(The\ slope-intercept\ formula:y=mx+b\\m\to the\ slope\\b\to y-intercept\\\\a)\\y=3x-4\\\\the\ slope:m=3\\\\y-intercept:(0;-4)\\\\b)\\4x-5y=15\\-5y=-4x+15\\y=\frac{4}{5}x-3\\\\the\ slope:m=\frac{4}{5}\\\\y-intercept:(0;-3)\)