The freezing point is $\displaystyle-{{249}}^{\circ}+{{148}}^{\circ}\usepackage{cmbright}\Huge\$ . First, find the difference of the absolute values: $\displaystyle{{249}}^{\circ}-{{148}}^{\circ}={{101}}^{\circ}\usepackage{cmbright}\Huge\$ . Since the negative addend has the greater absolute value, the sum will be negative.