We are told that the height of the ballon after t seconds is given by the equation
![\text{height}=120+2t](https://img.qammunity.org/2023/formulas/mathematics/college/yb20cnnpw12vce4odwkorrlj89fnt6vegp.png)
and we are asked to find the height after 15 seconds.
To answer this question we simply put in t =15 in the above formula to get
![\text{height}=120+2(15)](https://img.qammunity.org/2023/formulas/mathematics/college/dtxj0utetrllyz9frch7o2516auilrj5a2.png)
This gives
![\text{height}=120+30](https://img.qammunity.org/2023/formulas/mathematics/college/dwpytn4f4w62nexnrbdrb8f9nd3w836xgw.png)
![\text{height}=150m](https://img.qammunity.org/2023/formulas/mathematics/college/w1rgztln60ohbhtgzgff447vsr5ypq0fz2.png)
Hence, the height of the ballon after 15 s is 150m
.