[tex]\longrightarrow{\blue{20}}[/tex]
[tex]\large\mathfrak{{\pmb{\underline{\red{Step-by-step\:explanation}}{\red{:}}}}}[/tex]
[tex]\:15 + ( - 2) + 7[/tex]
➺ [tex] \: 15 - 2 + 7[/tex]
➺ [tex] \: 22 - 2[/tex]
➺ [tex] \: 20[/tex]
[tex]\sf\pink{PEMDAS\: rule.}[/tex]
P = Parentheses
E = Exponents
M = Multiplication
D = Division
A = Addition
S = Subtraction
[tex]\large\mathfrak{{\pmb{\underline{\orange{Happy\:learning }}{\orange{.}}}}}[/tex]