Задание 2986

$$0,2^{9-10x}=625$$

$$\left(\dfrac15 \right)^{9-10x}=5^4$$

$$5^{(-1)\cdot (9-10x)}=5^4$$

$$5^{10x-9}=5^4$$

$$10x-9=4$$

$$10x=4+9$$

$$10x=13$$

$$x=1,3$$