For equipment that I purchased that was installed at a client's office, how do I write that off? Or do I subtract it from the payments I received from them (1099)?

I did computer consulting on the side. I was hired to install new internet equipment. I paid for the equipment and the company paid me for both the equipment and the labor. Since labor and equipment are combined on one check, I am taxed on that income, but how do I offset the amount I paid for the equipment?