Given:
The cost price of two pieces of equipment was $2000.
The cost price of one is $770 more than the other.
To find the price of the less expensive piece of equipment:
Let x be the price of the less expensive piece of equipment.
That is, x+770 is the price of the other piece of equipment.
So, we write it as,

So, the price of the less expensive piece of equipment is $665.