The sum of two parts equal 90.
Also,
one part is 4 times the other part.
Let the normal part be "x", so the 4 times part would be "4x".
Their sum is 90, thus we can write:
[tex]x+4x=90[/tex]Solving for x (a part):
[tex]\begin{gathered} x+4x=90 \\ 5x=90 \\ x=\frac{90}{5} \\ x=18 \end{gathered}[/tex]The other part is:
90 - 18 = 72
So,
The two parts we separate 90 into are "18 and 72".
