How are the independent and dependent variables related?

Here number of pizza is the independent and cost of pizza toppings is the dependent variable because cost of pizza is dependent on the number of pizza toppings.

Notice that cost of pizza is increasing with increasing of pizza toppings like for one topping the cost is 14 and for 2 toppings cost has increased to 16.

So, independent and dependent variables are lineraly positively correlated.

the sum of all the angles in a triangle are equal to 180

so you can add   the 3 given angles together to equal 180:

5y + 2y + 2y = 180

or since all three angles have the same letter, combine the 3 angles to equal 180:

9y = 180