Simple calculation

[SlowHabit]

It's quite embarrassing that after so many hands of poker, I don't know how to do a simple equity calculation. Can you guys enlighten me?

Problem 1
Money already in pot: $1000
Villain's stack: $900
Hero's stack: $800

Villain's equity: 75%
Hero's equity: 25%

I make it hot on the flop and pushed. If Villain folds, I win $1000; ez moneys.

If Villain calls, his hand has an equity of $600. My hand has an equity of $450. Total, I lose $150 every time Villain calls.

So, the question is "what percentage of the time should Villain go away so I can break even?"

I use the following formula. Please correct me if I'm wrong. Thanks.

0 = 1000x + (1-x)(-150)

Problem 2:
Money already in pot: $1000
Villain's stack: $1000
Hero's stack: $1250

Villain's equity: 75%
Hero's equity: 25%

Problem 3
Money already in pot: $1950
Villain's stack: $1000
Hero's stack: $1250

Villain's equity: 75%
Hero's equity: 25%

Once again, thanks!