These require you solve for y. Do that by subtracting the x-term, then dividing by the y-coefficient.
5. 3y = 7x -9
y = (7/3)x -3
6. 6y = -2x -3
y = (-2/6)x -3/6
y = (-1/3)x -1/2
7. 8y = 2x + 12
y = (1/4)x +3/2
Let breadth(b) of rectangular be x
Then length(l) = 5x + 1
We have : perimeter(p) =2(l+b)
Or, p = 2 (5x+1+x)
p = 2 (6x+ 1)
p = 12x + 2
Given that p= 98 m
98=12x+2 i.e. x= 8
So breadth b= 8m and length l =5*8+1= 41m
6.74
7.69
5.92
6.68
i listed the unit prices in order and the lowest unit price is for the 10 oz one