John had 7 red marble and 5 blue marble in a box. Today, he put some marble in the box and the ratio is 10 red to 19 total. How many blue marbles does he put today in the box?

He added 14 blue marbles to the box today

10 - 19 =9 answer 9 blue marbles

Step-by-step explanation:

When club members will sell 2 cakes, sales will cover expenditure . sales for 2 cakes is $28 and expenditure for 2 cakes is $28. Required equations are  as follows  

x = 14y (equation for sale)  

x = 3y + 22 (equation for expenditure).

Solution:

Need to write a system of equations to describe given situation.

Given that  

Members of cooking club are making cakes to sell at street fair.

Selling price of a piece of cake = $14

Cost of booth at the fair = $22

Cost of ingredient for 1 cake = $3

we need to find a point where expenditure is equal to sale.

let say number of cakes be represented by variable y

So selling price of y cakes = selling price of 1 cake multiplied by y = 14 x y = 14y

COST OF y CAKES

Cost of ingredient of y cakes = cost of ingredient of 1 cake x y = 3 x y = 3y

Cost of the booth = $22

total cost of y cakes = Cost of ingredient + cost of booth = 3y + 22

Expenditure will cover when total cost is equal to selling price  

=> 14y = 3y + 22

On solving the above equation for y

=> 14y – 3y = 22

=> 11y = 22

=> y = 2  

So when club members will sell 2 cakes

Sale = 2 x 14 = $28

Expenditure (cost) = (3)2 + 22 = $28

So after selling 2 cakes expenditure will get covered.

Also given that club sale and expenditure will be $x once they have sold y cakes

=> x = 14y (equation for sale)  

And x = 3y + 22 (equation for expenditure).