Let's assume the number be x.
One fourth of a number, decreased by 10, is -50 can be converted into an algebraic equation as following:
[tex] \frac{1}{4} (x-10)=-50 [/tex]
[tex] \frac{1}{4} (x-10)*4=-50*4 [/tex] Multiply each sides by 4.
x-10=-200 (By simplifying)
x=-200+10 (Add 10 to each sides)
x=-190
So, the number is -190.