Why do you think this system reached equilibrium at a higher temperature?

increasing the temperature of the system ,will cause equilibrium to shift toward the direction of the reaction that absorbs heat.

Aquantity of that isotope to decay to 1/2 of  its original value

Those are different gas lawshere is a brief description of themcharles's law states that volume and temperature are directly proportional to each other as long as pressure is held constant.  boyle's law asserts that pressure and volume are inversely proportional to each other at fixed temperature.gay-lussac's law introduces a direct proportionality between temperature and pressure as long as it is at a constant volume.    source: