While an object is moving at a constant speed of 20m/s, a 5n forcé pushed the object to the left. at the same time a, 5n force is pushing the object to the right. what will the objects velocity be after 10 seconds

... We know that there are no forward or backward forces on the object, because its forward speed is constant.

... The left and right forces on the object add up to zero, so it won't begin to move left or right.  It'll just keep on with the same 20 m/s forward motion.

... Its velocity after 2 seconds, 10 seconds, or an hour, will still be 20 m/s forward.