Since you have y alone on one side of the equation......
Use substitution and plug in 1/2x-4 for y in the other equation.

Distribute

Combine like terms

Add 8 to both sides

Divide by 4
and 
Plug this value in for x

Simplify

Multiply everything by 8 and simplify

Divide.....

Your answers are:

Neutral atoms must have equal numbers of protons and electrons
Solution: 18 electrons
Sin θ = 2 / 7
tan θ > 0
cos θ = ?
sin θ = opposite / hypotenuse
tan θ = opposite / adjacent
cos θ = adjacent / hypotenuse
short leg = opposite = 2
hypotenuse = 7
long leg = adjacent = ?
adjacent = √(7² - 2²)
adjacent = √(49 - 4)
adjacent = √45
adjacent = √9 * 5
adjacent = 3 √5
cos θ = adjacent / hypotenuse
cos θ = 3√5 / 7
Answer:
Emilio compra kg De manzanas a euros el kilo cuanto pagara por Las manzanas