Answer:
The equation is 
The value of x is 28 cookies
Step-by-step explanation:
Let
x ----> the number of cookies she baked last week
we know that
The number of cookies she baked last week multiplied by 3 minus 4 must be equal to 80 cookies
so
The linear equation that represent this situation is

solve for x

He used 11/12 of sugar.
(1) I multiplied the factors and denominators by eachothers denominators
(2) I ended up with the two converted fractions: 8/12 and 3/12. The reason for this step is because if the two fractions have the smae denominator, it helps make it easier to add the fraction.
(3) I added the fractions, getting the sum of 11/12
Good question!
So first its 20 x 20 which is 400 so then the lawnmower does 80 per min so 80 x 5 and u get 400
The expression i determined is 10x + 6