If $X<Y$ then the CDF of $X$ greater then CDF of $Y$

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If $X$ and $Y$ two random varible with $$X\leq Y$$ then why $$F_X(x)\geq F_Y(y)$$ I have founded in paper.

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Suppose you know that if $A$ is true then so is $B.$ In that case $\Pr(A) \le \Pr(B).$

You have $X\le Y$ with probability $1.$

If $Y\le x$ then $X\le x.$

Therefore $\Pr(Y\le x) \le \Pr(X\le x).$

I.e. $F_Y(x) \le F_X(x).$