Compute 10*6+10-9/10*13.

An electrical light circuit in John's welding shop had a load of 2800 watts. He changed the circuit to ten 150-watt bulbs and six 100-watt bulbs. What fraction represents a comparison of the new load with the old load?

I have been quite confused by the definition of functions and their uses. First of all can one define functions in a clear understandable way, with a clear explanation of their uses, how they work and what they do?
Also I have some specific questions regarding functionsLet me give you a examples:
Also I have some specific questions regarding functions
Let me give you a examples:
1. ${\displaystyle y=f\left(x\right)\Rightarrow }$ This is one of the main reasons I have difficulties understanding functions...
What does the above statement tell me, and if y is a function why do we use ${\displaystyle y=}$ at all for a formula like ${\displaystyle y=mx+b}$ would it be the same as writing ${\displaystyle f\left(x\right)=mx+b?}$
2. Something like ${\displaystyle y=x^2}$ is apparently a function... but where is the function name? Which is the input and which is the output?
3. Lastly another example: Let me suppose ${\displaystyle f=}$ distance ${\displaystyle f\left(t\right)=t^2}$
${\displaystyle f\left(2\right)=4\Rightarrow }$ Does this mean distance is 4... which is the input which is the output?
Mainly what I'm looking for in an answer is a clear and 'easy' explanation with examples to help me understand this new topic

Adiba ate x fruit snacks. Faith ate ${\displaystyle \frac{3}{4}}$ less than that. Write an equation for the situation using fractions in your equation.

Describe two general methods to determine which of two fractions is greater. Use ${\displaystyle \frac{2}{3}\text{and}\frac{4}{5}}$ to illustrate the methods.

write the ratio as a fraction in lowest terms.
${\displaystyle 2\frac{3}{4}\text{ to }1\frac{1}{2}}$
${\displaystyle 2\frac{3}{4}\text{ is\_\_\_ \% of }1\frac{1}{2}}$

A polynomial P is given. (a) List all rational possible zeros (without testing to see whether they actually are zeros). (b) Determine the possible number of positive and negative real zeros using Descartes

simplify each numerical expression. ${\displaystyle -\frac{4}{5}-\frac{1}{2}\cdot (-\frac{3}{5})}$