Answer? Appreciate the help

Answer y = -2

Step 1.

In order to make an equation with 1 variable, substitute the right side of the first equation for x in the second equation for 3x + 5y = 20. In the example all instances of x in the second equation will be replaced by 10.

Rewrite the x so it will be 3 · 10.

3 · 10 + 5y = 20

Step 2.

Multiply 3 by 10.

3 × 10 = 30

Step 3.

Subtract 30 from both sides.

30 + 5y - 30 = 20 - 30

Step 4.

Simplify.

5y = -10

Step 5.

Divide both sides by 5.

1. Divide the numbers.

5 ÷ 5 = 1

= y

2. Simplify.

Apply the fraction rule.

3. Divide.

10 ÷ 5 = 2

Y = -2

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this