Answer
73$^{\circ}$J
Work Step by Step
1. Connect two scales into one expression
$\frac{J-17}{80}=\frac{H}{120}$
2. Simplify the expression multiplying both sides by 40
$\frac{J-17}{2}=\frac{H}{3}$
3. Given H=84, just substitute and solve for J:
$\frac{J-17}{2}=\frac{84}{3}$
$3J-51=168$
$3J=219$
$J = 73$
4. Therefore, boiling point of methanol in J scale is 73.
