we can start off by multiplying both sides by the LCD of all fractions, in this case that'd be 3.
[tex]\bf \cfrac{H}{3}+7=10\implies \stackrel{\textit{multiplying both sides by }\stackrel{LCD}{3}}{3\left( \cfrac{H}{3}+7 \right)=3(10)}\implies H+21=30\implies H=9[/tex]