(x+7)(y-15)=3
⇔ (x+7)y-15x-105=3
⇔ (x+7)y-15x-105-3=0
⇔ (x+7)y-15x-108=0
⇔ $\left \{ {{x+7=0} \atop {y-15=0}} \right.$
⇔ $\left \{ {{x=-7} \atop {y=15}} \right.$
320:(x-6)=2².5²-20
⇔ 320:(x-6)= 4.25-20
⇔ 320:(x-6)= 100-20
⇔ 320:(x-6)=80
⇔ x-6=320:80
⇔ x-6=4
⇔ x=4+6
⇔ x=10
$2^{5}$.x-23.x=5²-$2^{4}$
⇔ 32.x-23.x=25-16
⇔ 32.x-23.x=9
⇔ (32-23).x=9
⇔ 9x=9
⇔ x=1