take advantage of
To make good use of; to use well, to profit from.
The cat took advantage of the high grass to creep up on the bird.
Jean took advantage of the lunch hour to finish her homework.
I took advantage of my neighbour's superior skill at tennis to improve my own ability at the game.
To treat (someone) unfairly for your own gain or help; make unfair use of; to use another person’s weaknesses to gain what one wants.
He took advantage of his friend's kindness.
The little children did not know how much to pay for the candy, and Ralph took advantage of them.
Teddy is such a small, weak child that his friends take advantage of him all the time. They take advantage of him by demanding money and making him do things for them.