Question

4a - 3b , para a=3/12 e b= -1/4

Answer 1

Olá.

Montando as expressões e resolvendo temos:

$\mathsf{4\cdot\left(\dfrac{3}{12}\right)-3\cdot\left(\dfrac{-1}{4}\right)}\\\\\\\mathsf{\dfrac{12}{12}-\dfrac{-3}{4}=}\\\\\\\mathsf{\dfrac{12-3\cdot(-3)}{12}}\\\\\\\mathsf{\dfrac{12+9}{12}=}\\\\\\\boxed{\mathsf{\dfrac{21}{12}=1,75}}$

Qualquer dúvida, deixe nos comentários.
Bons estudos.