well.. [tex]\bf {{ a}}\%\ of\ b \implies \cfrac{{{ a}}}{100}\cdot b\implies {{ a}}\div 100\cdot b\\\\
-----------------------------\\\\
thus
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{{ 7.5}}\%\ of\ 10 \implies \cfrac{{{ 7.5}}}{100}\cdot 10\qquad and\qquad {{ 8}}\%\ of\ 10 \implies \cfrac{{{ 8}}}{100}\cdot 10[/tex]
get both, check their difference, that's how much more tax you'd be paying from 7.5% to 8% on $10
