Answer:
21x+6
Explanation:
first distrbute the 3 on the brackets
and note that in mathematics when there is no sign just like after the 3 it means it's multiplication
3(2x+5)+3(5x-3)
=6x+15+15x-9
now add or subtract
=21x+6
that is the simplest we can get and we can't find the value of x cuz this is not an equation
(there is no equal sign and numbers on both sides )