using the property of logarithms of log(a) b - log(a) c = log(a) (b/c) you get
log5 (4) -log5 (x-10) = 1 but 1 = log5 (5) so you can rewriting your exercise
log5 (4/(x-10)) = log5 (5) what mean that these are equal than
4/(x-10) = 5 multiple the right side by (x-10) and will get
4 = 5(x-10) but first of all make the condition that x not can being equal 10 bc. than this fraction will be undefined with denominator zero
4=5(x-10) so 4 = 5x -50 add to both sides 50 and will get
4+50=5x
54=5x divide both sides by 5
x = 54/5
x = 10,8
hope helped