## Intermediate Algebra (6th Edition)

$\left[ 3,\infty \right)$
Using the properties of inequality, the expression $0.8x+0.6x\ge4.2$ simplifies to \begin{array}{l} 10(0.8x+0.6x)\ge(4.2)10 \\ 8x+6x\ge42 \\ 14x\ge42 \\ x\ge3 .\end{array} In interval notation, the solution set is $\left[ 3,\infty \right)$.