Answer: x = 4
Explanation:

multiplied by common denominator
3(10 + 5x)(3) - 1(6x + 3)(5) = 9(15) reduced all fractions
90 + 45x - 30x - 15 = 135 distributed
15x + 75 = 135 simplified (added like terms)
15x = 60 subtracted 75 from both sides
x = 4 divided 15 from both sides