\(26.17+38.26+26.44+26=26\left(17+38+44+1\right)=26.100=2600\)

\(2^x=31-15=16=2^4\\ \Rightarrow x=4\)

\(b,\left(-26\right)+16+\left(-34\right)+26=\left(-10\right)+\left(-8\right)=-18\\ c,12+3.\left[39-\left(5-2\right)^2\right]\\ =12+3.\left[39-3^2\right]\\ =12+3.\left[39-9\right]\\ =12+3.30\\ =12+90=102\)

\(18:\left(-3\right)^2.2=18:9.2=2.2=4\)

Bà mua tất cả số gam báng và kẹo là:

\(125\times6+250\times1=1000\left(g\right)=1kg\)

D

\(B\left(420\right)=\left\{420;840;1260;...\right\}\)