The equation is $ 3x\equiv 33\pmod{100}$
I factored the 100 as $2^2 \cdot 5^2$ then I got the system of equations: $$3x \equiv 33\pmod 4$$ $$3x \equiv33\pmod{25}$$
then I transformed the equivalences into this two: $$3x \equiv 2 \pmod 4$$ $$3x\equiv8 \pmod{25}$$
And from there I don't know how to proceed.