a) `(15/10x+25):2/3=60`
$\dfrac{15}{10}x+25=60.\dfrac{2}{3}=40$
$\dfrac{15}{10}x=40-25=15$
$x=15:\dfrac{15}{10}$
$x=15.\dfrac{10}{15}=10$
Vậy $x=10$
b) Vì $0≤\dfrac{x}{5}≤2$ mà $x$ nguyên
$⇒\dfrac{x}{5}=\dfrac{0}{5},...,\dfrac{10}{5}$
$⇒x=0,1,...,10$
$⇒$ P={0,1,...,10}