Answer:
See explanations below
Step-by-step explanation:
Given the system of equation
2x - 10 y = -30 ... 1
x - 5y = 20 ... 2
Step: From 2;
x = 20 + 5y ...3
Step 2: Substitute equation 3 into 1
2x - 10y = -30
2(5y+20) - 10y = -30
Open the bracket
10y + 40 - 10y = -30
10y - 10y + 40 = -30
0+40 = -30
40 = -30
The steps taken by Teri are correct all through. He didn't make any error whatsoever
False........................
This is how I would do it, hope this helps!
Answer:

Step-by-step explanation:
A complex number is a number which has some real part and some imaginary part.
Standard form of a complex number is represented as

Where
is the real part,
and
is the imaginary part.
And 
Given complex number:

Hence, the standard form is
.
Answer:
The height of the tree is 3m