a ) t ( x + 15 ) = 20 b ) t x = 5 → t = 5 x {\displaystyle {\begin{aligned}&a)t(x+15)=20\\&b)tx=5\rightarrow t={\frac {5}{x}}\\\end{aligned}}}
a ) t ( x + 15 ) = 20 t = 5 x ↓ 5 x ( x + 15 ) = 20 5 x + 75 = 20 x 15 x = 75 x = 5 ↓ v = 5 k m h r v 2 = 5 + 15 = 20 k m h r {\displaystyle {\begin{aligned}&a)t(x+15)=20\\&{\color {blue}t={\frac {5}{x}}}\\&\downarrow \\&{\frac {5}{x}}(x+15)=20\\&5x+75=20x\\&15x=75\\&x=5\\\downarrow \\&v=5{\frac {km}{hr}}\\&v_{2}=5+15=20{\frac {km}{hr}}\\\end{aligned}}}
