Since y is 5.2 you can substitute it in your equations 5.2 = -5x - 40 then you do things like normal add 40 in both sides and divide -5 in both sides you get 9.04
8) 36 - 12x = 48
12x = -12
X= -1
9) x = 24.5
10) 5x -15 = 45
5x = 30
X =6
11) -3x+9=45
3x= -36
X= -12
12) 14y=21
Y= 1.5
13) 2m = 8/5
M= 4/5
14) 3x = 15
X= 5
(x² - (1/5x²))²
Using (a-b)² = a²-2×ab+b²
(x²)² -2x²×(1/5x)² + (1/5x²)²
x⁴ -2x⁴ + 1/25⁴
We developed the fraction to obtain the lowest common denominator
x⁴/1 - 2x⁴/5 +x⁴/25
25×(X⁴)/25×1 - 5×(2x⁴)/5×5 + x⁴/25
25×⁴/25 - 10x⁴/25 + x⁴/25
{25×⁴- 10x⁴ + 1x⁴}/25
{26×⁴- 10x⁴}/25
{26×⁴- 10x⁴}/25
16x⁴/25