Resposta:

a) 32

b) 30 objetos

c) Pedro: 15

Andre: 10

d) Caderno = R$12,00

Apostila = R$36,00

e) Filho = 10 anos

Pai = 40 anos

Explicação passo a passo:

a) [tex]2x+8=72\\2x=72-8\\2x=64\\x=64 \div 2\\x=32[/tex]

b) [tex]\frac{x}{2} +\frac{x}{3} =25\\\frac{3x}{6} +\frac{2x}{6} = 25\\\frac{5x}{6} +25\\5x= 25\times6\\5x= 150\\x= 150 \div 5\\x=30[/tex]

c) [tex]x+x+5=25\\2x=25-5\\2x=20\\x=20\div2\\x=10[/tex]

d) [tex]x=\frac{y}{3} \\x+y = 48\\\\y=48-x\\\\\\x=\frac{48-x}{3} \\3x=48-x\\3x+x=48\\4x=48\\x=48\div4\\x=12\\\\y=48-12\\y=36[/tex]

e) [tex]x+y=50\\x=4y\\\\4y+y=50\\5y=50\\y=50\div5\\y=10\\\\x=4\times10\\x=40[/tex]