The freezing point is $\displaystyle-{{185}}^{\circ}+{{126}}^{\circ}\usepackage{cmbright}\Huge\$ . You need to first find the difference of the absolute values: $\displaystyle{{185}}^{\circ}-{{126}}^{\circ}={{59}}^{\circ}\usepackage{cmbright}\Huge\$ . Since the negative addend has the greater absolute value, the sum will be negative.