How do you know that the valves on the washing machine are leaking?
If they are the typical gate valves like the one on the water heater, and the leak is coming from around the valve stem, you may just be able to tighten the packing nut. The packing nut is the very top HEX nut where the valve stem goes through. A few drops of oil here can also be helpful, as well as not opening the valve COMPLETELY or hard open to resistance. Oil the stem, work the valve back and forth a few turn, and gently tighten the packing nut to see if you can get the leak to stop.
If the valves are leaking through, as in won't shut off the water, the valve is bad and needs to be replaced.
Valve stem packing can also be purchased and the packing replaced, but this will require shutting off the water and taking the packing nut loose from the stem. Yeah, a little bit of work, but if you can't solder in new valves, it's the easiest fix.