Answer: 
Step-by-step explanation:
Given
Equation is 
Mila uses the first step as multiplication to make the coefficient of x, 1
Mila maybe have multiplied the whole equation by 2 i.e.

36j + j = 37j
Explanation.
You could translate this sum into a normal sebtence: I have 36 apples and add 1 apple more.
The sum will then be 36 apples + apple = 37 apples.
Replacing the word (in this explanation 'apple') by a letter learns us 36a + a = 37a
Hence 36j + j = 37j
120% of 590=1.20*590=708.
For x% of a number y, the answer is x/100*y.
This is a Fibonacci sequence
1; 1
1 + 1 = 2
1 + 2 = 3
2 + 3 = 5
3 + 5 = 8
next terms:
5 + 8= 13
8 +13 = 21
13 + 21 = 34