multiply the equation by 5 to get
5x - 5y - 5z = -15 now since 5y = 3x
5x - 3x - 5z = -15 multiply THIS equation by 1.6
8x -4.8x - 8z = -24 now since 8z = 3x
8x - 4.8x -3x = -24
x = -120
It is good if we can express everything in terms of x. Because it will become a linear equation in one variable.
In fact, we can. Manipulating the first equation:
3x = 5y
y = 3x/5 = 0.6 x
3x = 8z
z = 3x/8 = 0.375 x
Then, we plug these into the equation:
\(x-0.6x-0.375x=-3\)
We simplify the left hand side:
\(0.025x = -3\)
Changing that 0.025 into a fraction gives
\(\dfrac x{40} =-3\\ \)
We multiply 40 to both sides to get
x = -120.