The smaller triangle was dilated to form the larger triangle. what is the value of x? 6.9 7.5 10 11

We know that
scale factor=measure larger triangle/measure smaller triangle>18/12
scale factor=1.5
so
measure larger triangle=scale factor*measure smaller triangle

for the leg in the smaller triangle equal to 5
measure larger triangle=1.5*5> 7.5

the answer is
7.5