[tex]A = \sqrt{75}- \sqrt{12}\\
A= \sqrt{25\times3}- \sqrt{4\times3}\\
A = \sqrt{25}\times \sqrt{3}- \sqrt{4}\times \sqrt{3}\\
A= 5\sqrt{3}-2 \sqrt{3}\\
A=3 \sqrt{3} [/tex]
[tex]B = \sqrt{48}+ \sqrt{27}- \sqrt{243}\\
B= \sqrt{16\times3}+ \sqrt{9\times3} - \sqrt{81\times3} \\
B = \sqrt{16}\times \sqrt{3}+ \sqrt{9}\times \sqrt{3}- \sqrt{81}\times \sqrt{3}\\
B = 4 \sqrt{3}+3 \sqrt{3}-9 \sqrt{3}\\
B=-2 \sqrt{3} [/tex]
2)
a) incomplet
b)
[tex] \frac{2}{3}x=5\\\\
x=5: \frac{2}{3}\\\\
x=5\times \frac{3}{2}\\\\
x= \frac{15}{2} [/tex]