What temperature is 10 degrees lower than 7 degrees?

None of those temperatures will be measured in boiling water.

10 degrees F . . . not water at all; ice

55 degrees F . . . cool water, a refreshing drink

78 degrees F . . . 'tepid' water, room-temp, neither cool nor warm

112 degrees F . . . noticeably warm water, a hot bath

0 degrees F . . . not water at all; ice

Under normal pressure water boils at 212 degrees F, changing the pressure, will change the temperature at which water boils.