Помогите решить срочно очень важно !!!

${5}^{x + 1} + {5}^{ x} = 750$
$6 \times {5}^{x} = 750$
${5}^{x} = 125$
${5}^{x} = {5}^{3}$
$x = 3$

${2}^{ x} - {2}^{x - 2} = 3$
$3 \times {2}^{x - 2} = 3$
${2}^{x - 2} = 1$
${2}^{x - 2} = {2}^{0}$
$x - 2 = 0$
$x = 2$

Третье не могу, сорян

${7}^{5x} - {7}^{5x - 1} = 6$
$6 \times {7}^{5x - 1} = 6$
${7}^{5x - 1} = {7}^{0}$
$5x - 1 = 0$
$5x = 1$
$x = 0.2$